This invention relates to reinforced corrugated paperboard and more particularly to containers made of reinforced corrugated paperboard. This invention is particularly concerned with a reinforced bin for relatively heavy palletized loads which are to be moved from place to place.
The paperboard bin shown in U.S. Pat. No. 3,945,558 has found considerable use in the meat processing industry. Such a bin is preferably made of corrugated paperboard and may be of single wall or double wall construction. One use for such a bin is the temporary storage and the movement within a meat packing plant, or from plant to plant, of animal parts, including organs. The bin is palletized to facilitate handling. The load or cargo carried by the bin usually includes internal organs and animal liquids so that the cargo exhibits hydraulic characteristics. A loaded bin may typically carry as much as 1100 to 2500 pounds of animal parts and organs. A loaded bin tends to assume a circular shape, in plan view, under the influence of the hydraulic pressure imparted therein by its cargo.
The movement of a loaded palletized bin within a meat packing plant or from plant to plant invariably involves subjecting the bin to considerable acceleration and shock forces. Such forces create momentary peaks in the internal pressure which substantially raise the hoop stress in the walls of the container. The resulting peaks in hoop stress, which assume the greatest value in the lower portion of the container, may exceed the strength of the container walls. A tear of the outer liner may begin at an inherently weakened portion thereof, for example, at a score line. Once such a tear begins, the hoop stress becomes more concentrated at the root of the tear causing the tear to rapidly propagate upwards along the wall. The result is a catastrophic failure of the bin. Such failures are most likely to happen during an acceleration load or shock applied to the bin while it is being moved or when it is being trucked. The successive acceleration or shock forces may tend to increase the effective hoop stress in the lower portions of the bin several fold.
Patent U.S. Pat. No. 1,605,953 teaches a reinforced corrugated paper product. The reinforcement is in the form of a rectangular grid pattern of reinforcing strands sandwiched between two sheets of paper which form the liner of the corrugated paper product. Of necessity, one set of strands will be parallel to the flutes of the corrugated medium and the other set will be generally perpendicular to the corrugated medium. If a bin is constructed of such a corrugated paper product with the corrugated flutes preferably in a vertical direction, some of the vertically oriented reinforcing strands will fail to register with the flutes of the corrugated medium thereby doing little to enhance the strength of the container. On the other hand, the horizontal strands will be circumferentially aligned passing successively over each of the flutes of the corrugated medium. Such strands will tend to absorb the hoop stress to which a container made thereof may be subjected. However, as such stresses are successively applied, the horizontal strands will tend to cut through the medium or the liner because the length of each strand is essentially the same as the circumference of the container. Also, each strand is firmly held in place and lacks any elastic behavior. As a result, the usefulness of such a container is limited to a distinct load and number of successive acceleration loads and shocks.